1. Field of the Invention
The present invention pertains to an optical disk, e.g., a compact disk (CD), having a holographic security label applied in a recessed portion of the disk. The disk and holographic label in combination are useful as an enhanced security device for the disk.
2. Description of Related Art
Digital optical disks, e.g., compact disks, are widely used as media for valuable computer software and consequently are susceptible to counterfeiting efforts. The use of a hologram for identification purposes on an optical disk is known. In the majority of prior art references, such a hologram is a surface-relief hologram formed by a stamping process such that the hologram is an integral part of the disk. In this case, the hologram must withstand all processing conditions used in disk fabrication, such that significant limitations are placed on these processing conditions in order for the hologram to not undergo significant damage during processing. Prior art of this type is Japanese Patent Publication 11-306600 and German Patent DE 29620074 U1.
In a few cases in the prior art, there are disclosures of a hologram (which can be a volume-phase hologram) being formed independently with respect to fabrication of the digital optical disk and then being applied to a flat, non-recessed area of the disk. Disclosures of this type are German Patent DE 29620074 U1 and European Patent Publication EP 1102267. While forming the hologram independently of disk fabrication and then applying the hologram as a label to the fabricated disk is advantageous in not limiting the processing conditions for disk fabrication, there is a significant drawback to this approach in that the holographic label can often be easily removed intact by a forger and then reapplied intact to another disk having more valuable software encoded in it to convey the impression that a non-authentic disk is authentic. A holographic label applied in this manner thus has limited value as a security device.
There is a significant need for a holographic label that can be applied to a digital optical disk after fabrication of the disk as a security device and in a manner such that the label cannot be removed in a counterfeiting action without the label undergoing significant or even total degradation. The present invention provides a solution to this important need.
A disk has a holographic label applied to the disk as an enhanced security device in a manner such that the holographic label cannot be removed without significant or even total destruction of the label. The disk has a top surface and a bottom surface joined by a peripheral outer edge and an opposed inner edge that defines a circular hole at the center of the disk. The disk contains recorded information disposed between the outer edge and a circular hub adjacent the inner edge with the hub supporting the holographic label for the disk. The holographic label is photopolymerized film containing a hologram disposed in a recessed portion of the hub between the top and bottom surfaces, wherein the photopolymerized film containing the hologram is pressed into the recessed portion.
The holographic label can be any shape and can vary in size as a percentage of the hub size ranging from a very small percentage ( less than 1 percent) to 100 percent. Similarly, the recessed portion of the hub can vary in shape and size in relation to the whole hub in the same manner. In a preferred embodiment, the recessed portion comprises a donut-shaped opening below the top surface. In another preferred embodiment, the hologram is a volume phase hologram. In still another preferred embodiment, the hub is clear and a side of the photopolymerized film that is adjacent to the disk contains a graphic image.
The invention also includes a method of applying a holographic security label to a disk having a top surface and a bottom surface joined by a peripheral outer edge and an opposed inner edge that defines a circular hole at the center of the disk, the disk containing recorded information disposed between the outer edge and a circular hub adjacent the inner edge, comprising the steps of:
a) positioning photopolymerized film containing a hologram adjacent a recessed portion in the hub between the top and bottom surfaces; and
b) pressing the film into the recessed portion of the hub.
Preferred embodiments of the above method include 1) the method wherein the recessed portion comprises a donut-shaped opening below the top surface, 2) the method wherein the hologram is a volume phase hologram, and 3) the method wherein the hub is clear and a side of the photopolymerized film that is adjacent to the disk contains a graphic image.